CO2 Reduction by Photocatalysis on TiO2

CO2 Reduction by Photocatalysis on TiO2

Daibing Luo (Sichuan University, China), Wangjing Ma (Chinese Academy of Sciences, China), Liangzhuan Wu (Chinese Academy of Sciences, China) and Kazuya Nakata (Tokyo University of Science, Japan)
Copyright: © 2018 |Pages: 32
DOI: 10.4018/978-1-5225-3903-2.ch010
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This chapter focuses on the recent research progress on TiO2-based photocatalysts for CO2 reduction. The scope of this chapter for photoreduction of CO2 is set to focus on the most widely studied TiO2-based photocatalysts, composites, and systems since 1979. In addition, several important kinds of other related photocatalysts will be introduced briefly.
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Before a new popular energy source of clean style are available, fossil fuels, including combustible gas, crude oil, and coal currently are still the main sources for the production of useful chemicals and energy until now. Statistics shows that most of the produced energy was generated from fossil fuels since 2011, which will domain the energy source for a long time until around 2030 by a prediction referenced to a BP’s energy outlook. The energy demand in the world is forecasted with a growth by 36% from 2011 to 2030 (Kondratenko, Mul, Baltrusaitis, Larrazábal, & Pérez-Ramírez, 2013). As CO2 is a final product of the fossil combustion process, the back conversion and utilization of CO2 are essential areas of conservation of resources and the development of a sustainable society (Lewis & Nocera, 2006; Schlögl, 2015). Therefore, decreasing CO2 amount in the air is of significance to address problems relating to the ‘greenhouse effect’. On the other hand, it will be interesting when using CO2 as the chemical source in conversion to solar fuels (Gust, Moore, & Moore, 2009). Furthermore, solar fuels generated from CO2 have advantages in storage and manipulation in comparison with hydrogen technology (Huber, Iborra, & Corma, 2006; K.-F. Li, An, Park, Khraisheh, & Tang, 2014).

However, even great progress has been achieved on photocatalysis technology dealing how to obtain chemical energy from photo energy, conversion of CO2 is currently still a great challenge since CO2 has a very stable chemical bonding which demands significant energy breaking the bonding on special catalysts. Numerous researchers have realized CO2 can be converted into various carbonates, carboxylates, and carbamates by electrochemical or photochemical methods (Albero & García, 2016; Roy, Varghese, Paulose, & Grimes, 2010). To efficiently convert CO2 into ideal fuel products, suitable activation mechanisms and reaction conditions must be found. Until now, chemical reduction of CO2 requires a substantial energy input which limits the further development of CO2 reduction technology.

Recently, photocatalytic reduction of CO2 has attracted worldwide attention since its convenience, easy for controlling, low cost, and specified selectivity of organic production (Balzani, Credi, & Venturi, 2008; Morris, Meyer, & Fujita, 2009). This technology may ameliorate atmospheric CO2 levels meanwhile provide useful chemical products such as carbon monoxide (CO), methane (CH4), methanol (CH3OH), formaldehyde (HCHO), and formic acid (HCOOH) (D. Liu et al., 2012; L. J. Liu, Zhao, Andino, & Li; Roy et al., 2010). In addition, if combined with the synthesis by solar energy, the light-induced reaction of CO2 and H2O to prepare hydrocarbons is a green technology for the conversion of solar energy to chemical energy. And the overall footprint of CO2 is considered to be neutral if these hydrocarbons are generated from CO2 as feedstock (Gust et al., 2009). Although many semiconductors have been investigated as photo catalysts for CO2 reduction, TiO2 has been proved to be the most suitable photocatalyst with the highest photocatalysis efficiency due to its stability and its relatively favorable bandgap energy. Great efforts have been made to increase the photocatalytic performance of TiO2 for CO2 conversion by various strategies.

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